The invention relates to a double crucible system for the production of light conducting fibers.
It is already known to draw light conducting fibers from a double crucible. For example, the publicaton by H.G. Unger, "Optische Nachrichtentechnik", 1976 Berlin, describes a device of this type under the key word "double nozzle method" on pages 39 and 40.
Previously, light conducting fibers produced in accordance with the double crucible method possessed a predetermined ratio between the cross-sections of the fiber cores and the fiber casings. This ratio of the cross-sections was determined by the structure of the double crucible. In order to produce fibers having a different ratio of the casing and core cross-sections, it was previously necessary to employ a different double crucible.
As the double crucibles are generally manufactured from highly pure platinum or platinum-rhodium alloys in order to avoid pollution of the glass melts by the crucible material, double crucibles of this type are extremely expensive and this has an unfavorable influence upon fiber cost.